In the prior art, as a method for preparing optically active ((R) or (S))-β-amino acids and optically active ((S) or (R))-β-amino acid esters simultaneously from β-amino acid esters (racemic mixture) by using a hydrolase, it has been disclosed a method in which one of enantiomers of ethyl 3-benzyloxycarbonylaminobutanoate (racemic mixture) is selectively hydrolyzed in 1,4-dioxane to obtain an optically active 3-(S)-aminobutanoic acid ethyl ester and an optically active 3-(R)-aminobutanoic acid in the presence of a lipase originated from Candida antarctica, water and triethylamine (Tetrahedron Asymmetry, 8, 37 (1997)).
However, according to this method, there are problems that a reaction time is quite long, an equal amount of triethylamine to the substrate must be added as a third component to heighten optical purity of the object, and the like, and it is disadvantageous as an industrial preparation method.
Also, there is no description about hydrolysis of β-amino acid alkyl esters in which a substituent on a nitrogen atom is an aralkyl group according to the present invention.
Moreover, in the prior art, as a method for preparing an optically active ((R) or (S))—N-substituted 2-homopipecolic acid and an optically active ((S) or (R))—N-substituted 2-homopipecolic acid ester simultaneously from an N-substituted 2-homopipecolic acid ester (racemic mixture) by using a hydrolase, it has been disclosed a method in which one of enantiomers of methyl N-acetyl-2-homopipecolate (racemic mixture) is selectively hydrolyzed in the presence of a Pig liver esterase to obtain an optically active ((R) or (S))—N-acetyl-2-homopipecolic acid and an optically active ((S) or (R))—N-acetyl-2-homopipecolic acid ester (Can. J. Chem., 65, 2722 (1987)).
However, according to this method, there are problems that an amount of the hydrolase to be used is extremely large, optical purity of the objective material is low, and the like, and it is disadvantageous as an industrial preparation method.
An object of the present invention is to solve the above-mentioned problems and to provide a process for preparing an optically active β-amino acid and an optically active β-amino acid ester that is industrially advantageous in which an optically active ((R) or (S))—N-substituted β-amino acid and an optically active ((S) or (R))—N-substituted β-amino acid alkyl ester are obtained simultaneously with high yield and high selectivity from an N-substituted β-amino acid alkyl ester (racemic mixture) according to a simple and easy method.
Another object of the present invention is to solve the above-mentioned problems and to provide a process for preparing an optically active homopipecolic acid and an optically active homopipecolic acid ester that is industrially suitable in which an optically active ((R) or (S))—N-substituted 2-homopipecolic acid and an optically active ((S) or (R))—N-substituted 2-homopipecolic acid ester are obtained simultaneously with high yield and high selectivity from an N-substituted 2-homopipecolic acid ester (racemic mixture).